Evidence for Fermi-energy pinning relative to either valence or conduction band in Schottky barriers

1989 ◽  
Vol 40 (15) ◽  
pp. 10607-10610 ◽  
Author(s):  
J. Y. Duboz ◽  
P. A. Badoz ◽  
F. Arnaud d’Avitaya ◽  
E. Rosencher
2018 ◽  
Vol 83 (3) ◽  
pp. 30101
Author(s):  
Asghar Esmaeili ◽  
Mehdi Faraji ◽  
Somayyeh Karimi

We present a discussion regarding the conduction band non-parabolicity and the Fermi energy of Al doped ZnO (AZO) degenerate semiconductors using the higher orders of Fermi–Dirac (F-D) integrals. We find an analytical expression for Fermi energy, based on two-band k.p theory and modified Boltzmann's classical equation. We examine the accuracy of resulted expression using absolute error value.


2005 ◽  
Vol 865 ◽  
Author(s):  
Akimasa Yamada ◽  
Koji Matsubara ◽  
Keiichiro Sakurai ◽  
Shogo Ishizuka ◽  
Hitoshi Tampo Hajime ◽  
...  

AbstractThe reasons why the open circuit voltage (Voc) of high-x CuIn1-xGaxSe2 (CIGS)/ZnO solar cells remain low are discussed. Here it is shown that the Voc ceiling can be interpreted simply on the basis of a model that the valence-band energy (Ev) of CIGS is almost immovable irrespective of x. When the conduction-band energy (Ec) of ZnO is lower than that of high-x CIGS (DEc<0), the built-in potential (Vbi) of a CIGS/ZnO junction is equivalent to the flat-band potential (Vbi) that arises from the separation between the Fermi energies of the two materials. If the Ev (and therefore the Fermi energy) of p-type CIGS is constant with increasing x, the Vbi and Voc that follows the Vbi remain unchanged since the Fermi energy of ZnO is constant. This unchangeable Voc reduces the conversion efficiency of high-x CIGS cells in cooperation with reduced photocurrents due to a larger bandgap. A positive offset, ΔEc>o gives rise to a photoelectrons barrier in the conduction-band that partially cancels Voc, thus the Voc of a low-x CIGS cell is governed by the Ec of CIGS. Based upon this concept, a material selection guideline is given for the windows and transparent electrodes appropriate for high-x CIGS absorbers-based solar cells.


2001 ◽  
Vol 685 ◽  
Author(s):  
Kevin L. Jensen

AbstractThe effects of a Coulomb-like potential in the Schottky barrier existing between a material-diamond interface is analyzed. The inclusion is intended to mimic the effects of an ionized trap within the barrier, and therefore to account for charge injection into the conduction band of diamond via a Poole-Frenkel transport mechanism. The present treatment is to provide a qualitative account of the increase in current density near the inclusion, which can be substantial. The model is first reduced to an analytically tractable one-dimensional tunneling problem addressable by an Airy Function approach in order to investigate the nature of the effect. A more comprehensive numerical approach is then applied. Finally, statistical arguments are used to estimate emission site densities using the results of the aforementioned analysis.


1997 ◽  
Vol 493 ◽  
Author(s):  
J Robertson ◽  
C W Chen

ABSTRACTThe electronic structure of SrBi2Ta2O9 and related oxides such as SrBi2Nb2O9, Bi2WO6 and Bi3Ti4O12 have been calculated by the tight-binding method. In each case, the band gap is about 4.1 eV and the band edge states occur on the Bi-O layers and consist of mixed O p/Bi s states at the top of the valence band and Bi p states at the bottom of the conduction band. The main difference between the compounds is that Nb 5d and Ti 4d states in the Nb and Ti compounds lie lower than the Ta 6d states in the conduction band. The surface pinning levels are found to pin Schottky barriers 0.8 eV below the conduction band edge.


1997 ◽  
Vol 482 ◽  
Author(s):  
A. Sampath ◽  
H. M. Ng ◽  
D. Korakakis ◽  
T. D. Moustakas

AbstractIn this paper we report on the formation of ohmic contacts to n- AlxGa1-xN alloys. The films were produced by plasma-assisted MBE and doped n- type with silicon at doping levels between 1018 to 1019 cm-3. Contacts were formed by sequential deposition of 200 Å of Ti and 2000 Å of Al and the contact resistivities were determined from TLM measurements. For low Al- content (x<. 10) the I-V characteristics are linear with contact resistivities of between 10-4 to 10-5 cm2. The contacts become progressively non-ohmic at Al concentrations greater than 10%. There results are consistent with the Schottky limit being applicable to these alloys and thus the Ti/Al contact forms Schottky barriers with higher barrier height as the conduction band of the alloy moves towards the vacuum level.


1989 ◽  
Vol 163 ◽  
Author(s):  
H.D. Yao ◽  
A. Compaan

AbstractExtremely heavily doped n-GaAs was produced by pulsed-laser annealing of Si implanted GaAs, achieving carrier concentrations exceeding 3.2×1019/cm3. Our photoluminescence (PL) spectra indicate a bandgap narrowing due to heavy n-type doping with a functional form of Δεg(eV) = - 6.3 × 10cm-8[(cm-2)]1/3 . At the highest carrier concentration, the bandgap shrinkage reaches -200 meV and the electron Fermi energy is -410 meV. These large values indicate that there exists a considerable conduction band “stretch” between the Γ and L-valley of GaAs for very high n-type concentrations.


2001 ◽  
Vol 666 ◽  
Author(s):  
David L. Young ◽  
Timothy J. Coutts ◽  
Don L. Williamson

ABSTRACTSingle-phase, spinel zinc stannate (ZTO = Zn2SnO4) thin films were grown by rf magnetron sputtering onto glass substrates. Uniaxially oriented films with resistivities of 10−2 -10−3 ωcm, mobilities of 16 - 26 cm2/V-s, and n-type carrier concentrations in the low 1019 cm−3 range were achieved. X-ray diffraction peak intensity studies established the films to be in the inverse spinel configuration. 119Sn Mössbauer studies identified two octahedral Sn sites, each with a unique quadrupole splitting, but with a common isomer shift consistent with Sn+4. A pronounced Burstein-Moss shift moved the optical bandgap from 3.35 eV to as high as 3.89 eV.Density-of-states effective mass, relaxation time, mobility, Fermi energy level, and a scattering parameter were calculated from transport data. Effective-mass values increased with carrier concentration from 0.16 to 0.26 me as the Fermi energy increased from 0.2 to 0.9 eV above the conduction-band minimum. First-order nonparabolic conduction-band theory was applied to extrapolate a bottom-of-the-band effective mass of 0.15 me. Calculated scattering parameters and temperature-dependent transport measurements correlated well with ionized impurity scattering with screening by free electrons for highly degenerate films.


1992 ◽  
Vol 06 (05n06) ◽  
pp. 527-528
Author(s):  
A. ZAWADOWSKI ◽  
K. PENC ◽  
G.T. ZIMANYI

Orbital Kondo effect is treated in a model, where additional to the conduction band there are localized orbitals with energy not very far from the Fermi energy. If the hopping between the conduction band and the localized heavy orbitals depends on the occupation of the conduction band orbital then orbital Kondo correlation occurs. The assisted hopping vertex is enhanced due to the Coulomb interaction between the heavy orbital and the conduction band. The enhanced hopping results in mass enhancement and attractive interaction in the conduction band. The superconductivity transition temperature is calculated. The models of this type can be applied to the high- Tc superconductors where the non-bonding oxygen orbitals of the apical oxygens play the role of heavy orbitals. For an essential range of the parameters the Tc obtained is about 100K.


1995 ◽  
Vol 78 (5) ◽  
pp. 3367-3370 ◽  
Author(s):  
Nam‐Young Lee ◽  
Kyu‐Jang Lee ◽  
Chul Lee ◽  
Jae‐Eun Kim ◽  
Hae Yong Park ◽  
...  

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